Reversible alexia, mitochondrial myopathy, and lactic acidemia.

A 11-year-old boy of short stature had recurrent right temporal pounding headaches of 7 months' duration, and progressive visual loss for 3 days. There was a left hemianopia, alexia without agraphia, and diffuse muscle weakness. Investigation established the presence of a mitochondrial myopathy with pyruvate and lactic acidemia and increased serum content of sarcoplasmic enzymes. On treatment with prednisone, the patient's strength and reading skill improved, symptoms resolved, and muscle enzymes returned to normal. Three attempts to reduce steroids resulted in accentuation of symptoms, seizures, weakness, regression of reading skills, and elevation of serum enzymes. The alexia was also reversible.